Catalytic carbon for oxidation of carbon monoxide in the presence of sulfur dioxide

Abstract

A carbon supported catalyst used for carbon monoxide oxidation is chemically modified by treating the activated carbon support with an oxidizing agent and/or a hydrophobic compound prior to impregnation with the catalyst mixture. The thus treated catalytic carbon is capable of oxidizing carbon monoxide in an air stream containing sulfur dioxide over an extended period of time.

What we claim is: 
     
       1. In the method of preparing activated carbon supported catalysts for oxidation of carbon monoxide, comprising the step of impregnating an activated carbon support with a catalyst composition comprising one or more members selected from the group consisting of Cu, Cr, Ni, Fe, Mn, Au, Ag, Pt, Pd, Rh and oxides and chloride, hydroxide, carbonate and nitrate salts thereof, the improvement comprising the additional steps of, first, oxidatively modifying said activated carbon support by treating said carbon support with a fluid oxidizing agent prior to impregnating thereof with said catalyst, whereby oxygen is added to the surface of said activated carbon support in an amount of from about 1% to about 5% by weight of said activated carbon support and the reducing properties of said activated carbon support are substantially reduced,   provided that, where the oxidizing agent is an oxyacid, that the acid is employed in a concentration of from 1 to 15 weight %, and in an amount, expressed as a weight ratio of acid to activated carbon, of from 1:1 to 5:1, whereby weight loss from the activated carbon as a result of acid treatment does not occur,   and, second, impregnating said activated carbon support with an inert hydrophobic compound in an amount of from about 1% to about 20% by weight of said activated carbon, before the step of impregnating said activated carbon support with said catalyst composition,   said improvement resulting in an activated carbon supported catalyst having improved efficiency in the presence of sulfur dioxide.   
     
     
       2. The method of claim 1 wherein the hydrophobic compound is one or more members selected from the group consisting of aliphatic hydrocarbons of at least fourteen carbon atoms and aromatic hydrocarbons of at least ten carbon atoms. 
     
     
       3. An activated carbon supported catalyst produced by the method of claim 1. 
     
     
       4. The activated carbon supported catalyst of claim 3 wherein the hydrophobic compound is one or more members selected from the group consisting of aliphatic hydrocarbons of at least fourteen carbon atoms and aromatic hydrocarbons of at least ten carbon atoms. 
     
     
       5. In the method of preparing activated carbon supported catalysts for oxidation of carbon monoxide, comprising the step of impregnating an activated carbon support with a catalyst composition comprising one or more members selected from the group consisting of Cu, Cr, Ni, Fe, Mn, Au, Ag, Pt, Pd, Rh and oxides and chloride, hydroxide, carbonate and nitrate salts thereof, the improvement comprising the additional steps of, first, oxidatively modifying said activated carbon support by treating said carbon support with a fluid oxidizing agent prior to impregnating thereof with said catalyst, whereby oxygen is added to the surface of said activated carbon support in an amount of from about 1% to about 5% by weight of said activated carbon support and the reducing properties of said activated carbon support are substantially reduced,   provided that, where the oxidizing agent is an oxyacid, that the acid is employed in a concentration of from 1 to 15 weight %, and in an amount, expressed as a weight ratio of acid to activated carbon, of from 1:1 to 5:1, whereby weight loss from the activated carbon as a result of acid treatment does not occur,   and, second, impregnating said activated carbon support with an inert hydrophobic compound in an amount of from about 1% to about 20% by weight of said activated carbon, after the step of impregnating said activated carbon support with said catalyst composition,   said improvement resulting in an activated carbon supported catalyst having improved efficiency in the presence of sulfur dioxide.   
     
     
       6. The method of claim 5 wherein the hydrophobic compound is one or more members selected from the group consisting of aliphatic hydrocarbons of at least fourteen carbon atoms and aromatic hydrocarbons of at least ten carbon atoms. 
     
     
       7. An activated carbon supported catalyst produced by the method of claim 5. 
     
     
       8. The activated carbon supported catalyst of claim 7 wherein the hydrophobic compound is one or more members selected from the group consisting of aliphatic hydrocarbons of at least fourteen carbon atoms and aromatic hydrocarbons of at least ten carbon atoms.